<!DOCTYPE html>
<html lang="zh">
<head>
	<meta charset="UTF-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Document</title>
	<style>
		/* em   相对单位，相对父元素 */
		html{
			font-size: 16px;
		}
		div{
			font-size: 15px;
		}
	/* 	p{
			width: 10em;
			height: 10em;
		} */
		p{
			width: 12rem;
			height: 12rem;
		}
	</style>
</head>
<body>
	<div>
		<p>我会飞</p>
	</div>
</body>
</html>